1. Field of Invention
The present invention relates to a polarization luminaire for uniformly illuminating a rectangular illumination area or the like with polarized light waves in which the polarization direction thereof is made to be uniform. Further, the present invention relates to a projection display for modulating polarized light, which has been emitted from this polarization luminaire, by means of a light valve and for enlarging an image and displaying the image on a screen.
2. Description of Related Art
Hitherto, a system of the optical integrator using two lens plates has been known as an optical system for uniformly illuminating a rectangular illumination area of a liquid crystal light valve or the like. The system of the optical integrator is disclosed in, for example, Japanese Patent Public Disclosure No. 3-11806/1991 Official Gazette and has already been put to practical use.
Ordinary projection displays, which use liquid crystal light valves of the type adapted to modulate polarized light, can utilize only single kind of polarized light. It is, therefore, important for obtaining a light projected image to enhance the utilization efficiency of light.
An object of the present invention is to propose a luminaire suitable for using in a projection display or the like, which uses a liquid crystal light valve of the type adapted to modulate polarized light, as an illuminating system.
More particularly, the object of the present invention is to propose a polarization luminaire that is provided with a system of the optical integrator and a polarization conversion system and can efficiently utilize polarized light and further can achieve uniform illumination. Furthermore, another object of the present invention is to propose a projection display provided with this newly proposed polarization luminaire.
A polarization luminaire of the present invention has: a light source for emitting polarized lights whose polarization directions are random; and a system of the optical integrator that is provided with a first lens plate consisting of a plurality of lenses and with a second lens plate consisting of a plurality of lenses. The polarized light radiated from the light source is projected on the entrance plane of each of the lenses of the second lens plate through the first lens plate in such a manner as to form a secondary light source image thereon. Further, an object is radiated with light emitted from the second lens plate. This polarization luminaire of the present invention further has: polarized light splitting means for splitting a light emitted from the light source into two kinds of polarized lights whose polarization directions are perpendicular to each other and whose traveling directions are apart from each other by an angle of less than 90 degrees; and polarization conversion means for causing the two kinds of polarized lights to have the same polarization direction. Moreover, this polarization luminaire of the present invention employs a configuration in which the polarized light splitting means is placed on one of an entrance side and an exit side of the first lens plate of the system of the optical integrator.
Here, note that in the case where a region illuminated with polarized light emitted from the system of the optical integrator is oblong in the same manner as a rectangle or the like, it is preferable that a splitting direction, in which two lights split by the polarized light splitting means are separated from each other, is the direction of the length of the region.
Further, it is desirable that the shape of each of the lenses composing the second lens plate of the system of the optical integrator is similar to that of each of the lenses composing the first lens plate.
An element having a structure (namely, a liquid crystal structure), in which a liquid crystal layer is sandwiched between a prism substrate and a glass substrate and an interface between the liquid crystal layer and the prism substrate is formed as a multistage surface inclined at an angle of less than 90 degrees to the optical axis of the means, may be employed as the polarized light splitting means.
A prism beam splitter, which is provided with a polarized light splitting film constituted by a dielectric multi-layer film and is adapted to split a polarized light emitted from the light source, whose polarization direction is random, into two kinds of polarized lights, whose polarization directions are perpendicular to each other, and is further adapted to emit the two kinds of polarized lights respectively in directions forming a deviation angle of less than 90 degrees, may be employed, instead of this element using a liquid crystal, as the polarized light splitting means.
The following configurations can be employed as that of the prism beam splitter.
(1) A prism beam splitter having the following configuration can be employed. This prism beam splitter has a flat quadrangular prism and a triangular prism whose inclined surface portion is joined to one of opposed side surface portions of the quadrangular prism. In a joint portion between the quadrangular prism and the triangular prism, the polarized light splitting film is formed. A reflection film for reflecting single kind of polarized lights, which is transmitted by the polarized light splitting film, in a predetermined direction is formed on the other of the opposed side surface portions of the quadrangular prism.
As the aforementioned triangular prism, a triangular prism containing liquid can be employed.
(2) A prism beam splitter having the following configuration can be employed. This prism beam splitter has a first flat quadrangular prism and a second flat quadrangular prism whose side surface portion is joined to one of opposed side surface portions of the first quadrangular prism. In a joint portion between the first and second quadrangular prisms, the polarized light splitting film is formed. A reflection film for reflecting single kind of polarized lights, which is transmitted by the polarized light splitting film, in a predetermined direction is formed on the other of the opposed side surface portions of the first quadrangular prism.
(3) A prism beam splitter having the following configuration can be employed. This prism beam splitter has a flat quadrangular prism and a plurality of triangular prisms whose inclined surface portions are joined to one of opposed side surface portions of the quadrangular prism. In a joint portion between the quadrangular prism and the triangular prisms, the polarized light splitting film is formed. A reflection film for reflecting single kind of polarized lights, which is transmitted by the polarized light splitting film, in a predetermined direction is formed on the other of the opposed side surface portions of the quadrangular prism.
As the triangular prism described hereinabove, a triangular prism containing liquid can be employed.
(4) A prism beam splitter having the following configuration can be employed. This prism beam splitter has a first triangular prism, on the inclined surface of which the polarized light splitting film is formed, and a second triangular prism, on the inclined surface of which a reflection film for reflecting single kind of polarized lights, which is transmitted by the polarized light splitting film, in a predetermined direction is formed. While the first and second triangular prisms are in a state in which the space therebetween is filled with liquid, the first and second triangular prisms are formed in such a manner as to be integral with each other.
(5) A prism beam splitter having the following configuration can be employed. This prism beam splitter has a plurality of quadrangular-prism-like prism composite elements, each of which has: a flat quadrangular prism; a first triangular prism whose inclined surface portion is joined to one of opposed side surface portions of the quadrangular prism; and a second triangular prism whose inclined surface portion is joined to the other of the opposed side surface portions of the quadrangular prism. In each of the prism composite elements, the polarized light splitting film is formed in the joint portion between the quadrangular prism and the first triangular prism, and a reflection film is formed in the joint portion between the quadrangular prism and the second triangular prism. The prism composite elements are aligned in a line in a direction perpendicular to the optical axis of the system of the optical integrator in such a way that the polarized light splitting films become parallel. The reflection film reflects to output the randomly-polarized light having been emitted from the light source portion to the next prism on one side, and reflects the polarized light which is transmitted by the polarized light splitting film formed in the same prism composite element in a predetermined direction on the other side.
In this case, the prism composite elements are set in such a manner that the polarized light splitting films are inclined at about 45 degrees to the optical axis of the system of the optical integrator.
(6) A prism beam splitter having the following configuration can be employed. This prism beam splitter has a plurality of quadrangular-prism-like prism composite elements, in each of which the polarized light splitting film is formed. The prism composite elements are aligned in a line in a direction perpendicular to the optical axis of the system of the optical integrator in such a way that the polarized light splitting films extends nearly in the same direction.
(7) A prism beam splitter having the following configuration can be employed. This prism beam splitter has a plurality of quadrangular-prism-like prism composite elements, in each of which the polarized light splitting film is formed. The prism composite elements are aligned in a line in a direction perpendicular to the optical axis of the system of the optical integrator. Moreover, on both sides of the optical axis of the system of the optical integrator, the polarized light splitting films extend nearly in the opposite directions.
Incidentally, in the case that the prism beam splitter has a prism composite element as described above, the width measurement of this prism composite element can be set as follows. If each of the lenses composing the first lens plate of the system of the optical integrator is a rectangular lens, the width measurement of the prism composite element can be set at (1/n) of the width measurement of this rectangular lens (incidentally, n is an integer which is equal to or larger than 1).
Further, a deviation prism can be disposed between the polarized light splitting means and the system of the optical integrator. Alternatively, a deviation prism can be placed between the light source and the polarized light splitting means. In this case, the deviation prism can be formed in such a way as to be integral with an entrance side of the polarized light splitting means. Further, the deviation prism, the polarized light splitting means and the first lens plate of the system of the optical integrator may be formed as an element having a single-piece construction.
Next, in the case of employing a, prism beam splitter as the polarized light splitting means, the prism beam splitter may be disposed on the optical path between the first lens plate and the second lens plate, instead of being placed nearer to the light source side than the first lens plate of the system of the optical integrator. In this case, a prism beam splitter having the following configuration has only to be employed. Namely, this prism beam splitter has a flat quadrangular prism and a rectangular prism whose inclined surface portion is joined to one of opposed side surface portions of the quadrangular prism. In a joint portion between the quadrangular prism and the rectangular prism, the polarized light splitting film is formed. A reflection film for reflecting single kind of polarized lights, which is transmitted by the polarized light splitting film, in a predetermined direction is formed on the other of the opposed side surface portions of the quadrangular prism. The two orthogonally intersecting surfaces of the rectangular prism are used as a surface of incidence and an exit surface. Polarized light is incident on the surface of incidence thereof and is then split by the polarized light splitting film into two kinds of polarized lights that are subsequently reflected by the reflection film and are finally outputted from the exit surface thereof in such a manner as to be separated and outputted therefrom, respectively, at angles which are nearly symmetric with the optical axis.
In this case, after the first lens plate of the system of the optical integrator is disposed on the surface of incidence of the rectangular prism in a state, in which the first lens is joined thereto and further, the deviation prism is disposed at a position, which is nearer to the light source side than the position of the first lens, light emitted from the light source has only to be incident on the first lens plate at a certain angle of incidence which is not a right angle. Needless to say, the deviation prism may be disposed between the first lens plate and the surface of incidence of the rectangular prism. Alternatively, the deviation prism may be disposed between the exit surface of the prism beam splitter and the second lens plate.
Next, an optical system using first and second condensing mirror plates, each of which consists of mirrors, instead of the first lens plate may be employed as the system of the optical integrator. Namely, the polarization illumination device employing such an optical system has: a light source; a polarized light splitting means that has a structure, in which a polarized light splitting film constituted by a dielectric multi-layer film is sandwiched between two rectangular prisms, and is operative to split an output light of the light source into p-polarized light and s-polarized light, whose polarization directions are orthogonal to each other, by means of this polarized light splitting film; a first condensing mirror plate that comprises a plurality of condensing mirrors, each of which has a rectangular appearance, and is operative to condense the p-polarized lights emitted from the polarized light splitting means and to form a plurality of secondary light source images represented by the p-polarized lights; a second condensing mirror plate that has nearly the same size and shape as of the first condensing mirror plate and is operative to condense the s-polarized lights emitted from the polarized light splitting means and to form a plurality of secondary light source images, which are represented by the s-polarized lights, at positions slightly different from positions where the plurality of secondary light source images represented by the p-polarized lights are formed; first and second quarter-wave plates that are disposed between the first condensing mirror plate and the polarized light splitting means and between the second condensing mirror plate and the polarized light splitting means; and a light condenser lens plate, which comprises lenses of the same number as of the condensing mirrors composing the first or second condensing mirror plate, and a half-wave plate that are placed in the vicinity of the positions, at which the plurality of secondary light source images represented by the p-polarized lights are formed, and the positions at which the plurality of secondary light source images represented by the s-polarized lights are formed.
Here, note that a deviation prism can be formed between the light source and the polarized light splitting means.
Further, deviation prisms can be disposed between the polarized light splitting means and the first condensing mirror plate and between the polarized light splitting means and the second condensing mirror plate, respectively.
In the case of using a deviation prism, the deviation prism may be formed in such a manner as to be integral with the polarized light splitting means. Further, the deviation prism may be formed in such a way as to be integral with the first condensing mirror plate. Alternatively, the deviation prism may be formed in such a way as to be integral with the second condensing mirror plate.
The polarized light splitting means can be constituted by a flat polarized light splitting plate.
Further, a liquid-filled prism may be used as the rectangular prism composing the polarized light splitting means.
Moreover, in the case that a region illuminated with polarized light emitted from the system of the optical integrator is oblong in the same manner as a rectangle or the like, it is preferable that a separating direction, in which two kinds of secondary light source images formed by the two condensing mirror plates are separated from each other, is made to coincide with the direction of the length of the region.
Furthermore, it is desirable that the shape of each of the lenses composing the condenser lens plate is similar to that of each of the condensing mirrors composing the first and second lens plates.
Next, in the case that a prism beam splitter is employed as the polarized light splitting means, a configuration, in which the prism beam splitter may be placed within the second lens plate, may be employed, instead of the configurations, in which the prism beam splitter is disposed at a position nearer to the light source than the first lens of the system of the optical integrator as above described, and in which the prism beam splitter is disposed on the optical path between the first lens plate and the second lens plate as stated above.
The polarization luminaire of the present invention having the former configuration instead of the latter configurations comprises: a light source for emitting polarized lights, whose polarization directions are random; a first lens plate that comprises a plurality of condenser lenses, each of which has a rectangular appearance, and is operative to condense polarized lights emitted from the light source and to form a plurality of secondary light source images represented by the polarized lights; a second lens plate that is placed in the vicinity of a position, at which the plurality of secondary light source images are formed, and has a condenser lens array, a polarized light splitting prism array, a half-wave plate and an exit side lens; the condenser lens array comprises condenser lenses of the same number as of the condenser lenses composing the first lens plate; the polarized light splitting prism array being operative to split a polarized light, whose polarization direction is random, into a p-polarized light and an s-polarized light and comprises a plurality of polarizing beam splitters and a plurality of reflecting mirrors; the half-wave plate being placed on the side of the exit surface of the polarized light splitting prism array; and the exit side lens being disposed on the side of the exit surface of the half-wave plate.
In this case, it is similarly desirable that the shape of each of the condenser lenses composing the second lens plate is similar to that of each of the condenser lenses composing the first lens plate.
Further, a deviation prism can be placed between the light source and the first lens plate. In this case, the deviation prism can be formed in such a way as to be integral with the first lens plate.
Moreover, lenses of a decentered system may be used as the condenser lenses composing the first lens plate. Similarly, decentered lenses may be used as the condenser lenses composing the condenser lens array of the second lens plate.
Furthermore, it is preferable that the lateral width of each of the condenser lenses composing the condenser lens array of the second lens plate is made to be equal to that of the polarizing beam splitter.
Incidentally, the quarter-wave and half-wave plates used in each of the aforementioned configurations can be made of TN (twisted nematic) liquid crystals.
On the other hand, the present invention relates to a projection display provided with a polarization luminaire having each of the aforesaid configurations. Namely, a projection display that comprises: a luminaire; a modulation means having a liquid crystal light valve which is operative to modulate polarized light included in luminous flux radiated from this luminaire and to cause the light to contain image information; and a projection optical system for throwing the modulated luminous flux onto a screen and for displaying an image thereon, wherein the luminaire has each of the aforesaid configurations.
Here, note that projection displays are roughly classified into devices of a type (particularly, referred to as a single-plate type), each of which uses a single liquid crystal light valve, and devices of another type, each of which uses a plurality of liquid crystal light valves and that in the case of attaching importance to the brightness and the display quality of an image, the projection display of the latter type using a plurality of liquid crystal light valves is usually used. The projection display using a plurality of liquid crystal light valves is required to split luminous flux according to the number of the liquid crystal and thus needs a mechanism therefor.
Therefore, an ordinary projection display has: a color light splitting means for splitting luminous flux, which is radiated from the luminaire, into at least two luminous fluxes; and light synthesis means for synthesizing a synthetic luminous flux from the modulated luminous flux after modulated by the modulation means, wherein the synthetic luminous flux obtained by the color synthesis means is applied to a screen through the projection optical system and a color image is displayed thereon.